Hi there thanks for writing in, This bump or mass can be a couple of things.
Your dog has anal sacs located at approximately the three and seven o'clock postitions when viewing his anus. Sometimes these sacs can become infected or impacted and cause some discomfort. If the impaction or infection goes on long enough and becomes severe enough it can become an abscess and eventually form a draining tract. So the swelling you are seeing may be due to a enlarged/ full anal gland. This can sometimes be treated by manually expressing the sacs to empty the contents and a course of antibiotics. Sometimes surgical removal of the sacs are needed if it the impaction/infection is severe.
Another possibility is that the bump is actually a tumor. There are cancerous and non-cancerous tumors in this location. In intact male dogs will sometimes develop a hormone dependent non cancerous growth next to their anus. These masses sometimes resolve just by have the dog neutered but surgical removal may also be needed. Worst case scenario is that this a malignant tumor involving the anal sac tumor.
So the best thing to do is to bring your dog into your regular vet and have take sample of this bump and look at it under a microscope to determine if it is a cancerous/non cancerous tumor or anal gland issue.
Hope this helps and good luck
Really the only thing you can do at this point, is have him stop licking his anus. You can use an Elizabethan collar (the dreaded lampshade), they are available at most pet stores (Petsmart I know has them), just call before you make a trip.
Also, depending on what they determine is the problem for the bump, that will determine your expense.
An anal gland abscess will require flushing of the wound and some antibiotics.
If they feel it is more of a tumor, then a cytology will be necessary and that varies vet to vet but most likely 60-100 dollars. If you are concerned with cost, simply ask for an estimate prior to them performing any diagnostics.
Now my dog has puss coming out of the lump. Does that change what it could be or is there anyhting I can do to keep it from leaking or stoppin git?
If there's pus coming from the area then its starting to sound more and more like an abscessed anal gland. You can apply warm compresses to the area. You want to encourage drainage so we don't want to stop it.
See your vet tomorrow
Thanks for the follow up.
what causes an abcessed anal gland
They get impacted if material in them is abnormally thick and the dog can't express them normally.
Any further questions should be directed to your vet tomorrow.
Thanks for the updates!